This book will be the first comprehensive and systematic account of the modes and reasons for which the profile of Giacomo Leopardi (1798-1837) has undergone a radical shift from poet to philosopher since the publication of the Zibaldone in 1898-1900. An extraordinary text of over 4,500 manuscript pages written in the course of 15 years, the Zibaldone has acquired the status of an international masterpiece, especially since its 2013 translation into English. This book will not only be a history of the editorial and critical fortune of Leopardi’s notebook to its very latest developments, but it will also delve into the network of historical factors (political, economic, technological) that have transformed Leopardi’s notebook from a key-work for the interpretation of its author in Italy into a reference point for European philosophical thought.